Last Julio-Claudian emperor (4)
I believe the answer is:
nero
'last julio-claudian emperor' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for nero that I've seen before include "Emperor (who fiddled while Rome burned?) d. AD68" , "Roman arsonist and fiddler" , "Barbarous Roman emperor" , "Emperor said to have fiddled as Rome burned" , "Roman Emperor, 54-68 AD" .)